Evaluating Postural Control and Ankle Laxity Between Taping and High-Top Cleats in High School Football Players.

CONTEXT: Lateral ankle sprains are the most common injuries in high school sports. While ankle taping is a preferred method of external prophylactic support, its restrictive properties decline during exercise. The Under Armour® Highlight cleat is marketed on the premise that it provides added support without the need for additional ankle taping. OBJECTIVE: To determine if differences in ankle joint laxity and postural control exist between football players wearing the Under Armour® Highlight cleat (Under Armour Inc, Baltimore, MD) as compared to a low/mid-top cleat with ankle tape. DESIGN: Crossover trial. SETTING: Athletic training room and football practice field sideline. PATIENTS: 32 interscholastic football players (15.8 ± 1.0 y; 178.9 ± 7.4 cm; 87.1 ± 21.4 kg). INTERVENTIONS: Ankle laxity was assessed using an instrumented ankle arthrometer (Blue Bay Research Inc, Milton, FL), while postural control testing was performed on the Tekscan MobileMat™ Balanced Error Scoring System (BESS; South Boston, MA). The 2 treatments included Under Armour® Highlight cleats and a low/mid-top cleat with ankle tape applied to the nondominant ankle only. Measurements were taken before and immediately after practice. MAIN OUTCOME MEASURES: The independent variable was treatment (Highlight vs low/mid-top cleat with ankle tape). Dependent variables included ankle arthrometry measures of anterior displacement (mm), inversion/eversion rotation (deg), and the modified BESS error scores. A linear mixed-effects model was used for analysis. RESULTS: The low/mid-top cleat with tape condition had significantly higher inversion range-of-motion (ROM) and inversion/eversion rotation postexercise when compared to the Highlight cleat (P < 0.05). CONCLUSIONS: The results of this study provide some evidence that the Under Armour® Highlight cleat restricts ankle ROM following a training session better than the taped low/mid-top cleat. Further study is warranted to determine if this high-top style of football cleat can reduce the incidence of ankle sprains and how it might compare to spat taping.

The Effect of Shoulder Plyometric Training on Amortization Time and Upper-Extremity Kinematics.

CONTEXT: Plyometric training is credited with providing benefits in performance and dynamic restraint. However, limited prospective data exist quantifying kinematic adaptations such as amortization time, glenohumeral rotation, and scapulothoracic position, which may underlie the efficacy of plyometric training for upper-extremity rehabilitation or performance enhancement. OBJECTIVE: To measure upper-extremity kinematics and plyometric phase times before and after an 8-wk upper-extremity strength- and plyometric-training program. DESIGN: Randomized pretest-posttest design. SETTING: Research laboratory. PARTICIPANTS: 40 recreationally active men (plyometric group, age 20.43 ± 1.40 y, height 180.00 ± 8.80 cm, weight 73.07 ± 7.21 kg; strength group, age 21.95 ± 3.40 y, height 173.98 ± 11.91 cm, weight 74.79 ± 13.55 kg). INTERVENTION: Participants were randomly assigned to either a strength-training group or a strength- and plyometric-training group. Each participant performed the assigned training for 8 wk. MAIN OUTCOME MEASURES: Dynamic and static glenohumeral and scapular-rotation measurements were taken before and after the training programs. Dynamic measurement of scapular rotation and time spent in each plyometric phase (concentric, eccentric, and amortization) during a ball-toss exercise were recorded while the subjects were fitted with an electromagnetic tracking system. Static measures included scapular upward rotation at 3 different glenohumeral-abduction angles, glenohumeral internal rotation, and glenohumeral external rotation. RESULTS: Posttesting showed that both groups significantly decreased the time spent in the amortization, concentric, and eccentric phases of a ball-toss exercise (P < .01). Both groups also exhibited significantly decreased static external rotation and increased dynamic scapular upward rotation after the training period (P < .01). The only difference between the training protocols was that the plyometric-training group exhibited an increase in internal rotation that was not present in the strength-training group (P < .01). CONCLUSION: These findings support the use of both upper-extremity plyometrics and strength training for reducing commonly identified upper-extremity-injury risk factors and improving upper-extremity performance.

Adaptations of the Shoulder to Overhead Throwing in Youth Athletes.

CONTEXT: The high number of repetitions and high forces associated with overhead throwing lead to anatomical adaptations, such as humeral retrotorsion and posterior-capsule thickness, in elite and professional baseball athletes. However, little is known about the origin and progression of these changes that may account for the increasing trend of chronic shoulder injuries in youth baseball and precipitate subsequent pathologic conditions throughout a young athlete's lifetime. OBJECTIVE: To investigate the relationship of age and upper extremity dominance on humeral retrotorsion, posterior-capsule thickness, and glenohumeral range of motion. DESIGN: Cross-sectional study. SETTING: Research laboratory, local baseball fields, and training facilities. PATIENTS OR OTHER PARTICIPANTS: Thirty-six boys (mean age = 10.94 ± 1.34 years, height = 151.31 ± 12.17 cm, mass = 42.51 ± 10.32 kg) ranging in age from 8 to 12 years and involved in organized youth baseball. MAIN OUTCOME MEASURE(S): Diagnostic ultrasound was used to determine humeral retrotorsion and posterior-capsule thickness. Glenohumeral internal rotation and external rotation were measured using a handheld inclinometer. We used 2 × 2 mixed-model analyses of variance to compare the influence of limb dominance and age on the dependent variables of humeral retrotorsion, posterior-capsule thickness, internal rotation, and external rotation. RESULTS: The dominant shoulders of youth throwers exhibited less glenohumeral internal rotation but greater humeral retrotorsion, posterior-capsule thickness, and glenohumeral external rotation than the nondominant shoulders. Dominant internal rotation was greater in the 8- to 10-year-old group than in the 11- to 12-year-old group, and results trended toward a difference (F1,33 = 4.12, P = .05). Correlations existed between humeral retrotorsion and range of motion (P < .05). CONCLUSIONS: The structural adaptations in the dominant shoulders of younger baseball players were similar to adaptations observed in older baseball athletes, indicating that more examination is needed in younger athletes. We are the first to demonstrate greater posterior-capsule thickness in the dominant shoulders of youth baseball athletes.

The use of shear thickening nanocomposites in impact resistant materials.

The work presented here demonstrates using a novel, field-responsive nanocomposite based on shear thickening fluids (STFs) as responsive protective materials with superior damping and energy adsorption properties. Peak forces and accelerations measured using an instrumented Instron drop tower demonstrate that STF nanocomposite prototypes and impact foam taken from a commercial football helmet have similar performance for low kinetic energy impacts. However, tests with STF nanocomposite samples exhibit significantly reduced peak acceleration and peak force for impacts above 15 J. Thus, the STF containing nanocomposite material provides improved energy adsorption upon impact as compared to the commercial foam. These tests suggest that STF nanocomposite materials have promising potential as novel energy dissipating components in personal protective equipment.

Effect of elastic taping on postural control deficits in subjects with healthy ankles, copers, and individuals with functional ankle instability.

BACKGROUND: Ankle sprains are the most common injury among physically active people, with common sequelae including repeated episodes of giving way, termed functional ankle instability. Copers are a cohort in ankle research comprised of those who have sprained their ankle but have not suffered any further dysfunction. The use of an elastic tape, Kinesio Tape, in sports medicine practice has recently gained popularity and may help improve postural control deficits related to functional ankle instability. The purpose of this study was to examine the immediate and prolonged effects of Kinesio Taping on postural control in healthy, coper, and unstable ankles as measured through single-limb balance on a force plate. METHODS: Sixty physically active, college-aged participants (72.5 ± 9.7 cm, 74.2 ± 16.2 kg, 21.5 ± 2.6 years) were stratified into healthy, coper, or unstable groups using the Cumberland Ankle Instability Tool (CAIT) combined with their history of ankle injury. Dependent variables included time-to-boundary (TTB) measures and traditional center of pressure (COP) measures in both the mediolateral (frontal) and anteroposterior (sagittal) planes. Testing was performed prior to tape application, immediately after application of the tape, 24 hours following tape application, and immediately after tape removal. RESULTS: Significant differences between groups were observed for COP standard deviation and range in the sagittal plane. Significant differences between tape conditions for TTB absolute minima and standard deviation were also noted. Post hoc testing revealed large to medium effect sizes for the group differences and very small effect sizes for the differences between conditions. CONCLUSIONS: Our study did not reveal decisively relevant changes following application of Kinesio Tape to the ankle. However, we did observe sagittal plane postural control deficits in subjects with ankle instability measured through summary COP variables over 20-second trials. CLINICAL RELEVANCE: Ankle instability is a concern for many clinicians. Kinesio Taping, although a popular form of clinical intervention, remains understudied. Evidence from this study does not support the use of Kinesio Taping for improving postural control deficits in those with ankle instability.

Change in glenohumeral rotation and scapular position after a Division I collegiate baseball season.

CONTEXT: Pathologies such as anterior instability and impingement are common in baseball and have been linked to decreases in internal-rotation (IR) motion and concurrent increases in external-rotation (ER) motion. In addition, alterations to scapular upward rotation have been identified in this population. OBJECTIVE: To measure glenohumeral (GH) IR and ER rotation, total range of motion (ROM), and scapular upward rotation throughout the course of a Division I collegiate baseball season. DESIGN: Pretest to posttest study. SETTING: Controlled laboratory setting. PARTICIPANTS: Thirty-one collegiate baseball players with no current shoulder or elbow injury completed this study. INTERVENTION: Participants were measured for all dependent variables at preseason and postseason. MAIN OUTCOME MEASURES: GH IR and ER were measured supine with the scapula stabilized. Total GH ROM was calculated as the sum of IR and ER measures. Scapular upward rotation was tested at rest, 60°, 90°, and 120° of GH abduction in the scapular plane. RESULTS: Overall, the dominant arm had significantly less GH IR and significantly more ER than the nondominant arm. The total motion on the dominant arm was significantly less than on the nondominant arm. No significant differences were observed from preseason to postseason for IR, ER, or total motion. Dominant-arm scapular upward rotation significantly decreased at 60°, 90°, and 120° of abduction from preseason to postseason. CONCLUSION: Collegiate baseball players presented with significant GH-motion differences (decreases in IR and increases in ER) in their dominant arm compared with their nondominant arm. There was also significantly less total motion on the dominant arm. After 12 wk of competitive Division I collegiate baseball, there were significant decreases in upward rotation over the season.

Neuromuscular and stiffness adaptations in division I collegiate baseball players.

To compare bi-lateral shoulder EMG, active and short range glenohumeral stiffness, and examine its correlation to posterior capsule thickness (PCT) in collegiate baseball players. Surface and fine wire EMG was recorded on shoulder and scapular musculature during stiffness testing. Posterior capsule thickness was assessed separately using a diagnostic ultrasound. Serratus anterior EMG area and peak on the dominant arm was significantly greater compared to the non-dominant arm. The dominant arm had significantly greater active and short range glenohumeral stiffness compared to the non-dominant arm. Active glenohumeral stiffness was significantly correlated with PCT, however short range glenohumeral stiffness was not significantly correlated with PCT. Healthy collegiate baseball players present with adaptations of their stiffness regulation strategies. There were also correlations between stiffness and morphologic changes. Our results support the theory that PCT has an impact on the energy absorption capabilities of the shoulder during the deceleration phase of throwing. It also seems that tightening of the series elastic component within the posterior rotator cuff may be causing the increase in short range stiffness on the dominant arm.

Examining neuromuscular control during landings on a supinating platform in persons with and without ankle instability.

BACKGROUND: Ankle instability is a costly public health concern because of the associated recurrent sprains. It is evident there are neuromuscular control deficits predisposing these individuals to their ankle "giving way." Individuals with a history of lateral ankle sprain, who did not develop instability, may hold the key to understanding proper neuromuscular control after injury. HYPOTHESES: On the basis of previous research, the authors hypothesized that individuals with ankle instability would demonstrate reduced peroneal activation, causing a more inverted position of the ankle, before and after landing. STUDY DESIGN: Controlled laboratory study. METHODS: This study aimed to evaluate preparatory and reactive neuromuscular control when landing on a custom-designed ankle supinating device in individuals with ankle instability (AI), individuals with a history of lateral ankle sprains without instability (LAS), and uninjured controls (CON). Forty-five participants (15 per group) were asked to land on a device built to simulate the mechanism of a lateral ankle sprain (supination) while kinematics and muscle activity of the lower extremity were monitored. RESULTS: Contrary to our hypotheses, the AI group displayed significantly increased preparatory (P = .01) and reactive (P = .02) peroneal activation, while the LAS group demonstrated a trend toward increased preparatory tibialis anterior muscle activation (P = .07), leading to a decreased plantar flexion of the ankle at landing. CONCLUSION: The AI group was likely acting in a protective fashion to a potentially injurious situation, indicating these individuals can activate the peroneals if needed. The LAS group's strategy may be a safer strategy in that a less plantar-flexed position of the ankle is more close-packed and stable. Further, it appears the long-latency response of the peroneals may be enhanced in these individuals, which indicates motor learning at the supraspinal level to promote dynamic restraint. CLINICAL RELEVANCE: Individuals with AI can increase peroneal activation when necessary to dynamically stabilize the ankle, indicating the potential for training/rehabilitation. Further, the LAS group may deploy a different control strategy after injury to protect the ankle from subsequent sprains, which deserves investigation during activities of daily living. A greater understanding of these strategies will lead to the development of more appropriate treatment paradigms after injury to minimize the incidence of instability.

Internal rotation and scapular position differences: a comparison of collegiate and high school baseball players.

CONTEXT: Conditions such as labral and rotator cuff injuries have been linked with decreases in glenohumeral internal-rotation and increases in external-rotation motion. Also, decreased glenohumeral internal rotation is strongly associated with scapular dyskinesis. OBJECTIVE: To compare healthy collegiate and high school baseball players' glenohumeral joint range of motion and scapular position. DESIGN: Cross-sectional study. SETTING: Institutional research laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty-one male National Collegiate Athletic Association Division I collegiate (age = 20.23 +/- 1.17 years, height = 186.24 +/- 5.73 cm, mass = 92.01 +/- 7.68 kg) and 21 male high school baseball players (age = 16.57 +/- 0.76 years, height = 180.58 +/- 6.01 cm, mass = 79.09 +/- 11.51 kg). MAIN OUTCOME MEASURE(S): Glenohumeral internal and external rotation and scapular upward rotation were measured with a digital inclinometer. Scapular protraction was measured with a vernier caliper. All variables except scapular upward rotation were calculated as the difference between the dominant and nondominant sides. RESULTS: Collegiate baseball players had more glenohumeral internal-rotation deficit (4.80 degrees, P = .028) and total motion deficit (5.73 degrees, P = .009) and less glenohumeral external-rotation gain (3.00 degrees, P = .028) than high school players. Collegiate baseball players had less scapular upward rotation than high school players at the 90 degrees (4.12 degrees, P = .015, versus 3.00 degrees, P = .025) and 120 degrees (4.00 degrees, P = .007, versus 3.40 degrees, P = .005) positions. The scapular protraction difference was greater in collegiate baseball players than in high school players in the hands-on-hips and 90 degrees positions (0.77 cm, P = .021, and 1.4 cm, P = .001). CONCLUSIONS: When comparing high school with collegiate baseball players, these data suggest that glenohumeral internal-rotation deficit and scapular position change as the level of competition increases.

Internal rotation deficits affect scapular positioning in baseball players.

BACKGROUND: Anecdotal evidence suggests an association between glenohumeral internal rotation deficits (GIRD) and scapular dysfunction, an observable alteration in the normal position or motion of the scapula in relation to the thoracic cage. QUESTIONS/PURPOSES: We therefore hypothesized players with GIRD (15 degrees or greater) will have decreased dominant arm scapular upward rotation and increased scapular protraction compared with baseball players with GIRD (14 degrees or less). METHODS: We studied 43 baseball players with no current shoulder or elbow symptoms; 22 had GIRD 15 degrees or greater and 21 had GIRD 14 degrees or less. We measured glenohumeral internal rotation supine with the scapula stabilized. Scapular upward rotation was tested at rest; 60 degrees , 90 degrees , and 120 degrees abduction in the scapular plane; and scapular protraction at 0 degrees , hands on hips, and 90 degrees abduction in the scapular plane. RESULTS: The GIRD (15 degrees or greater) group had less scapular upward rotation at 60 degrees (3.58), 90 degrees (5.01), and 120 degrees (2.63) in the dominant arm. Scapular protraction at 90 degrees (0.88 cm) also was greater in the dominant arm of the GIRD (15 degrees or greater) group. CONCLUSIONS: Baseball players with more GIRD have alterations to the position and motion of their scapula. A dual goal of minimizing GIRD and strengthening the scapular stabilizers may be warranted in this population. LEVEL OF EVIDENCE: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

The evaluation of electrodermal properties in the identification of myofascial trigger points.

OBJECTIVES: To determine whether skin resistance measurements can objectively identify the location of myofascial trigger points (MTPs) and to differentiate between 3 states. DESIGN: Static group comparison. SETTING: Climate-controlled laboratory. PARTICIPANTS: Forty-nine participants (age, 20.5+/-2.6 y) were assigned to 1 of 3 groups based on clinical examination result: absent (n=21), latent (n=16), or active (n=12) MTP. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Skin resistance (in kilo-ohms). RESULTS: The 16 data points were divided into 3 categories for analysis: MTP site, surrounding tissue proximal to the MTP (first ring), and area furthest from the MTP (second ring). There was a significant increase in skin resistance between the MTP (403.64+/-124.73 kOmega), first ring (419.66+/-123.04 kOmega), and second ring (454.61+/-163.19 kOmega) (P<.01). The measurements did not differ significantly between the 3 MTP states. CONCLUSIONS: The changes in skin resistance between the MTP and the surrounding tissue support the inclusion of this technique to help identify MTPs. The similarity between MTP states warrants investigation into the physiologic differences at specific anatomic locations.

Effectiveness of prophylactic hyperextension elbow braces on limiting active and passive elbow extension prephysiological and postphysiological loading.

STUDY DESIGN: Experimental 3-factor design with repeated measures on all factors. OBJECTIVES: The purpose of this study was to determine the effectiveness of 3 prophylactic hyperextension elbow braces on limiting active and passive elbow extension before and after exercise. BACKGROUND: Prophylactic hyperextension elbow braces are used to protect the joint against excessive extension, but their effectiveness for this purpose has not been determined. METHODS AND MATERIALS: Twenty Division I intercollegiate football players (mean +/- SD age, 20.2 +/- 1.3 years; mean +/- SD height, 184.4 +/- 9.9 cm, mean +/- SD mass, 102.9 +/- 22.0 kg) completed all phases of the study. The Breg Functional Elbow Brace, PRO 470 Kendall Elbow Brace, and DonJoy Elbow Guard were tested both actively and passively before and after an isokinetic exercise session on a Biodex Multi-Joint Testing and Exercise Dynamometer. For all tests, the braces were set at a 30 degrees flexion limit angle. The exercise session consisted of 1 set of reciprocal elbow extension and flexion at an angular velocity of 360 degrees/s, totaling 1627 J of work. RESULTS: None of the braces limited elbow extension to the 30 degrees flexion limit. However, all of the braces were successful in preventing the elbow from reaching the vulnerable position of hyperextension. The Breg Functional Elbow Brace was the most effective for limiting elbow extension near its set angle, followed by the DonJoy Elbow Guard, and the PRO 470 Kendall Elbow Brace across all test conditions. CONCLUSION: The braces' effectiveness to limit motion is enhanced when limits are set higher than the desired angle of the protected motion.